Tunable Visible Light Emission of Self-Assembled Rhomboidal Metallacycles

Abstract

Supramolecular coordination complexes (SCCs) have been proposed for applications necessitating photon emitting properties; however, two critical characteristics, facile tunability and high emission quantum yields, have yet to be demonstrated on SCC platforms. Herein, a series of functionalized <i>D</i>_2<i>h</i> [D₂A₂] rhomboids (D = 2,6-bis­(4-ethynylpyridine)­aniline-based ligands; A = 2,9-bis­[<i>trans</i>-Pt­(PEt₃)₂NO₃]­phenanthrene) is described with emission wavelengths spanning the visible region (λ_max = 476–581 nm). Tuning was achieved by simple functional group modifications <i>para</i> to the aniline amine on the donor building block. Steady-state absorption and emission profiles were obtained for each system and are discussed. When the Hammett σ_<i>para</i> constants for the functional groups <i>para</i> to the aniline amine were plotted versus the wavenumber (cm^–1) for the λ_max of the emission profile, a linear relationship was observed. By utilizing this relationship, the emission wavelength of a given rhomboid can be predetermined on the basis of the Hammett constant of the functionality employed on the donor precursor. This range of visible light emission for a suite of simple rhomboids along with the predictive nature of the wavelength of emission is unprecedented for these types of systems